The present disclosure relates to an image processing apparatus that executes color correction on image data.
In recent years, image forming apparatuses (image processing apparatuses) with a color printing function, such as copying machines or multi-function peripherals (MFPs), have been commonly used. For example, image forming apparatuses with a color printing function implement color printing by combining printings by recording agents such as toner or ink of four colors of cyan (C), magenta (M), yellow (Y), and black (K).
Conventionally, image forming apparatuses are required to reliably reproduce a color of an original image.
In recently years, as an image including a photograph or the like can be printed, a function of converting a color of an image to print into a color preferred by human also started to be required.
For this reason, many of image forming apparatuses with a color printing function have a function of performing color correction on image data (for example, a related art 1).
Here, converting a color into a color preferred by human specifically means reproducing a so-called memory color. For example, the memory color refers a color such as a skin of human, the blue of the sky, the green of vegetation, and the red of sunset. The memory color is not a color faithfully reproduced from an original image, but a color, close to a color remembered by human, which human desires it to be reproduced.
In color correction for reproducing the memory color, correction of emphasizing a specific color, brightness correction, and the like may be executed at the same time. For example, when the blue of the sky which is pale blue close to a aqua blue is approximated to the memory color (deep blue), a user first changes a distribution state of blue within a range of a color gamut (an area where color reproduction is made) of blue, and executes color correction of emphasizing blue. Next, when the entire image looks dark as a result of emphasizing blue to be approximated to the memory color, the user further performs correction of brightening the entire image. However, in such image correction, color balance of a hue or the like may change by correction of brightness, and a color adjusted by blue emphasis correction may be deviated from a preferred color.
The related art 1 discloses a technique in which, among image correction parameters for color correction, brightness correction, sharpness correction, contrast correction, and the like, corrected images in which two different kinds of parameters are mutually changed and non-corrected images are displayed in the form of a matrix, and the user can select a desired image. According to the related art 1, a desired image is selected from among a plurality of images corrected by mutually changing a plurality of parameters. Since a correction parameter to apply can be decided, a desired image can be relatively easily acquired.
Meanwhile, it is known that there is a regional difference in a color preferred by human. In order to cope with such a regional difference, a technique of implementing color correction according to an installation region has been employed in image forming apparatuses which are sold in foreign countries as well as Japan (related arts 2 and 3).
For example, the related art 2 discloses an image processing apparatus that includes a plurality of output color tables classified according to an installation region of an apparatus and a user's race, and changes an output color table to use according to the user's request. Further, the related art 3 discloses an image processing apparatus that includes output profiles respectively corresponding to a plurality of regions, and uses an output profile obtained by synthesizing the output profiles at a synthesis ratio instructed by the user.
Meanwhile, when color correction is executed on some areas in image data, a pseudo contour may be generated in the boundary between the areas, or a tone becomes unnatural. As a countermeasure against this phenomenon, the related art 4 discloses an image forming apparatus in which a color correction coefficient differs according to a memory color. In this technique, when a memory color on which the user desires to put the most emphasis at the time of color reproduction is selected from among memory colors included in an original image, color correction is executed using a color correction coefficient corresponding to the selected memory color.
However, the above-described color correction of changing the distribution state of the specific color (blue in the above example) within the range of the color gamut is executed on all of pixels configuring image data. For this reason, the correction is reflected in the entire image. In the above example, since blue is emphasized on all pixels configuring image data, pixels including a blue component become more bluish. That is, the correction process corrects even a color of a portion to which color correction is not desired to be applied.
For example, when the above color correction is executed in an image forming apparatus with a function of designating an area, on which image correction is executed, in image data of a correction object, the drawback of the above correction process may be solved by employing a configuration of allowing the user to designate an area on which color correction is to be executed. However, when this configuration is employed, the work by the user is extremely complicated. Further, when a complicated process is necessary for designating an area, one user occupies the image forming apparatus for a long time. Thus, when the image forming apparatus is shared in an office or the like, work efficiency of all users who share the image forming apparatus is lowered.
Further, when the technique disclosed in the related art 4 is employed, color correction is executed using a dedicated color correction coefficient associated with the selected memory color. For this reason, color correction needs to be independently executed, and thus, for example, it is difficult to execute another color correction on the entire image data at the same time.
Meanwhile, when the techniques disclosed in the related arts 2 and 3 are employed, a memory color corresponding to a regional difference can be reflected in color correction. However, since the technique disclosed in the related art 2 is configured to change only the output color table according to the region, it is difficult to confirm whether or not the selected output color table matches with its own image until a printed material is output. In addition, the user's request may not be satisfied by the output color table arranged in the image processing apparatus. Furthermore, the technique disclosed in the related art 3 is configured to synthesize the output profiles arranged in the image processing apparatus at an arbitrary ratio. Thus, the number of selectable output profiles increases compared to the technique disclosed in the related art 2. However, since it is configured to change the synthesis ratio of the output profiles for a specific region previously arranged in the image processing apparatus, it is difficult to cover a regional difference in the user's favorite color.